RFR: 8258588: MD5 MessageDigest in java.util.UUID should be cached [v3]

[PROgrm_JARvis]

> Please review this change moving lookup of MD5 digest in `java.lang.UUID` to an internal holder class.

PROgrm_JARvis has updated the pull request incrementally with two additional commits since the last revision:

 - 8258588: add Md5MessageDigestLookup benchmark
 - 8258588: make UUID#Md5Digest thread-safe using ThreadLocal

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1821/files
  - new: https://git.openjdk.java.net/jdk/pull/1821/files/37db4c56..1abb7cfe

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1821&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1821&range=01-02

  Stats: 87 lines in 2 files changed: 77 ins; 5 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1821.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1821/head:pull/1821

PR: https://git.openjdk.java.net/jdk/pull/1821